| Summary: | 博士 === 國立交通大學 === 材料科學與工程系所 === 98 === Nanotecnology has been wildly used for biological applications. One of the most interesting examples is the so-called superhydrophobic surface. This type of structure is influenced by material property (hydrophbicity) and surface mophorogy (nanostructures). Since most cells can’t express celluar behavior without adhere on surfaces, it is very important to investiget the cellular adhesion on surface. For example osteoclast cells have to attach on the bone to behave normally. To understand the cell-substrate interactions, it is very important to investigate how cells adhere to the substrates and how the substrates respond to forces exerted by cells. There are two parts in this thesis; one is using low toxcisity polymeric nanostructure with different morphology to study the celluar adhesion behavior by it. Further more, the cell can be controlled to pattern on seleted area, as cell arrays. In the second part, the three dimentional periodic nano-porous structure in the integrated microfludic channel was used to study single DNA behavior.
In the first part of the dissertation, there were two simple techniques to impart superhydrophobic properties to the surfaces of microdevices. In the first approach, thin films of a fluoropolymer were spin-coated on the device surfaces followed by an oxygen plasma treatment. By varying the oxygen plasma treatment time, the water contact angles
on device surface could be tuned from 120° to 169°. In the second approach, a nanoimprint process was used to create nanostructures on the devices. To fabricate the nanoimprint stamps with various feature sizes, nanosphere lithography was employed to produce a monolayer of well-ordered close-packed nanoparticle array on the silicon surfaces. After oxygen plasma trimming, metal deposition and dry etching process, silicon stamps with different nanostructures were obtained. These stamps were used to imprint nanostructures on hydrophobic coatings, such as Teflon, over the device surfaces. The water contact angle as high as 167° was obtained by the second approach.
In the second part of this dissertation, the patterned nanostructure fluropolymer surfaces were used for the study of the cell adhesion. By a combination of photolithography and oxygen plasma treatment, patterned fluropolymer surfaces with various roughnesses have been obtain. The water contact angles measured on the surface were range from 120° to 163°, and surface roughness was measured from 2 nm to 65 nm. When these pattern surfaces were used as the substrates for the cell cultures of HeLa, NIH3T3, and CHO cells, it was found that those cell lines did not adhere to the flat fluropolymer surfaces. However, the number of NIH3T3 and CHO cells adhered on the surfaces increase with the surface roughness. Such nanostructure materials could be used as scaffold for selected cell growth.
In the third part of this dissertation, I will describe an approach to fabricate addressable cell microarrays, which are based on the patterned switchable superhydrophobic surfaces. The switchable superhydrophobic surfaces were prepared by roughening the surface of fluoropolymers on the electrodes. Upon the application of 150 V, the water contact angle on the roughened fluoropolymer surface could be changed from 1630 to less than 100 allowing the deposition of fibronectin, which could guide the growth of the cell. To patten the cells on such device,the HeLa cell was first seeded on pre-patterned fibbronectin area for incubatoring. After 3 hours incubation and removing suspension cell, the NIH 3T3 cell was incubated on same chip. Two different cell lines can be patterned on the same chip using the technique.
In the last part of this dissertation, I will describe a simple approach to fabricate robust three-dimensional periodic porous nanostructures inside the microchannels. In this approach, the colloidal crystals were first grown inside the microchannel using an evaporation-assisted self-assembly process. Then the void spaces among the colloidal crystals were filled with epoxy-based negative tone photoresist. After subsequent development and nanoparticle removal, thewell-ordered nanoporous structures inside the microchannel could be fabricated. Depending on the size of the colloidal nanoparticles, periodic porous nanostructures inside the microchannels with cavity size of 330 and 570 nm have been obtained. The dimensions of interconnecting pores for these cavities were around 40 and 64 nm, respectively. The behavior of single λ-phage DNA molecules in these nanoporous structures was studied using fluorescence microscopy. It was found that the length of DNA molecules oscillated in the nanoporous structures. The measured length for λ-phage DNA was larger in the 330 nm cavity than those measured in the 570 nm cavity.
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